Saturday, February 15, 2003. Henry Perowne is a contented man - a successful neurosurgeon, the devoted husband of Rosalind, and proud father of two grown-up children. Unusually, he wakes before dawn, drawn to the window of his bedroom and filled with a growing unease. As he looks out at the night sky, he is troubled by the state of the world - the impending war against Iraq, a gathering pessimism since 9/11, and a fear that his city and his happy family life are under threat.

Later, as Perowne makes his way through London streets filled with hundreds of thousands of anti-war protestors, a minor car accident brings him into a confrontation with Baxter, a fidgety, aggressive young man, on the edge of violence. To Perowne's professional eye, there appears to be something profoundly wrong with him. But it is not until Baxter makes a sudden appearance as the Perowne family gathers for a reunion, that Henry's fears seem about to be realised.